For some 20+ years in the middle of my speakers, but set back, I had a vertical Solid steel vertical rack with first the supplied MDF shelving, then over time various thick wooden cutting boards (John Boos, etc), and a couple exotic shelves made with violin wood. However, the height of the rack bugged me as I was convinced it was messing with the sound stage and imaging. A couple years ago I got the urge to go horizontal with maple (IMO) quartz/granite/glass, etc ring: YMMV, but it was way too expensive, but I got super lucky and found someone selling a DIY solid maple table for $200!. The top is ~ 50 x ~ 28 x2. Not only was it more visually appealing, but the both the imaging, sound stage and warmth that was missing from the vertical rack improved in a huge ways
See my Virtual System photos of both
hth